Garage insulation

[fastsvo]

Hey guys,

I'm about to insulate and drywall my garage and paying close attention to my east-facing wall because the sun is so against here in SoCal.

Currently the original tar paper is broken up or missing in several spots. My guy said the right way to do this is to remove the wood siding on the exterior side of the wall but this would be cost prohibitive. Is it worth stapling and patching the tar paper from inside the garage? I understand it's my only form of a vapor barrier while I don't see much rain here and my eaves are pretty deep, its still a concern.

That being said moving forward from the tar paper I'm interested in using some kind of polyiso board or perhaps a reflective atticfoil to work in unison with the R15 bats that I'm going to staple in. Would like to hear any suggestions or ideas on little tricks that I can do here before I close up this wall.

Thanks in advance!

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[ForceFed70]

I can't see how you could do a good job of replacing the tar paper from the inside.

That paper is intended to be a moisture barrier. Think of it like trying to successfully patch a roof from inside the attic.

If you think the siding is going to get hot (darker color) then the reflective barrier could certainly be a good addition.

 

[Voi]

That being said moving forward from the tar paper I'm interested in using some kind of polyiso board or perhaps a reflective atticfoil to work in unison with the R15 bats...

Foil faced poly-iso and I assume all of the attic foil type products are also vapor barriers. If your tar paper is intact in sections you'll have a possible moisture trap.

Is a vapor barrier required in garages by code in your area? If so is it specifically required to be on the exterior in your climate?

 

[lowe.joshua51]

I came accross this video recently, seems like a similar situation?

 

[K'ledgeBldr]

SoCal- why the insulation? Are you going to climate-control the garage?

 

[fastsvo]

Primarily trying to keep the heat out of the garage and maybe perhaps install a mini split in the future. I'm going to cover existing vents in the garage yet the sealed attic space above will have its own solar attic fan and two o'hagan vents for intake.

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[ebonyswan]

I would be considering stripping the siding, sheathing the wall and adding foam sheet on top of the sheathing before re-siding it. Done properly the foam is your vapor barrier. No thermal bridging with the foam on top of the sheathing either.

 

[fastsvo]

I would be considering stripping the siding, sheathing the wall and adding foam sheet on top of the sheathing before re-siding it. Done properly the foam is your vapor barrier. No thermal bridging with the foam on top of the sheathing either.

How about adding foam from the inside instead?

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[stm317]

Closed cell Spray foam can be a vapor barrier if sprayed a couple of inches thick.

 

[Voi]

How about adding foam from the inside instead?

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Here is an article that discusses just that. As I recall it's considered to be a safer practice in your climate than in my climate.

http://www.greenbuildingadvisor.com/articles/dept/musings/walls-interior-rigid-foam

I assume you'd want to remove as much of the original tar paper as possible.